U.S. patent application number 15/292512 was filed with the patent office on 2017-02-02 for light receiving device.
The applicant listed for this patent is Panasonic Intellectual Property Management Co., Ltd.. Invention is credited to Toshitaka AKAHOSHI, Masato KOBAYASHI, Manabu USUDA.
Application Number | 20170033142 15/292512 |
Document ID | / |
Family ID | 54323737 |
Filed Date | 2017-02-02 |
United States Patent
Application |
20170033142 |
Kind Code |
A1 |
KOBAYASHI; Masato ; et
al. |
February 2, 2017 |
LIGHT RECEIVING DEVICE
Abstract
A light receiving device includes: a photoelectric converter
including a photodiode and a first pixel electrode disposed on a
lower surface of the photodiode; a scanning circuit connected to
the first pixel electrode; an electrode pad disposed on a periphery
of the scanning circuit; a transparent conductive film extending
from an upper surface of the photodiode to the electrode pad, the
transparent conductive film having an inclination relative to the
upper surface of the photodiode, between the photodiode and the
electrode pad; and a sealing resin filled in a space between the
photoelectric converter and the scanning circuit, and in a space
under the transparent conductive film around the photoelectric
converter.
Inventors: |
KOBAYASHI; Masato; (Shiga,
JP) ; USUDA; Manabu; (Hyogo, JP) ; AKAHOSHI;
Toshitaka; (Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Panasonic Intellectual Property Management Co., Ltd. |
Osaka |
|
JP |
|
|
Family ID: |
54323737 |
Appl. No.: |
15/292512 |
Filed: |
October 13, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2015/001975 |
Apr 8, 2015 |
|
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15292512 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 31/0203 20130101;
H01L 31/022466 20130101; H01L 27/14618 20130101; H01L 31/107
20130101; H01L 21/563 20130101; H01L 2224/49175 20130101; H01L
27/14634 20130101; H01L 27/1469 20130101; H01L 27/14636 20130101;
H01L 27/14623 20130101 |
International
Class: |
H01L 27/146 20060101
H01L027/146; H01L 21/56 20060101 H01L021/56; H01L 31/0224 20060101
H01L031/0224 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 18, 2014 |
JP |
2014-086009 |
Claims
1. A light receiving device comprising: a photoelectric converter
including a photodiode and a pixel electrode disposed on a lower
surface of the photodiode; a scanning circuit connected to the
pixel electrode; an electrode pad disposed on a periphery of the
scanning circuit; a transparent conductive film extending from an
upper surface of the photodiode to the electrode pad, the
transparent conductive film having an inclination relative to the
upper surface of the photodiode, between the photodiode and the
electrode pad; and a sealing resin filled in a space between the
photoelectric converter and the scanning circuit, and in a space
under the transparent conductive film around the photoelectric
converter.
2. The light receiving device according to claim 1, wherein the
inclination is at 45 degrees or less.
3. The light receiving device according to claim 1, wherein the
scanning circuit includes a housing, the housing has a side surface
surrounding the photoelectric converter and having an inclination
relative to the upper surface of the photodiode, and the
transparent conductive film is formed on the side surface of the
housing.
4. The light receiving device according to claim 1, wherein the
pixel electrode and the scanning circuit are connected by a
microbump.
5. The light receiving device according to claim 4, wherein the
sealing resin reaches an edge of the upper surface of the
photodiode.
6. The light receiving device according to claim 4, wherein the
sealing resin partially covers the upper surface of the
photodiode.
7. The light receiving device according to claim 6, wherein the
sealing resin partially covering the upper surface of the
photodiode has a light shielding effect for the photodiode.
8. The light receiving device according to claim 1, further
comprising a unit for applying, to the photodiode, a voltage having
a magnitude which causes a charge multiplication effect in the
photodiode.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a U.S. continuation application of PCT
International Patent Application Number PCT/JP2015/001975 filed on
Apr. 8, 2015, claiming the benefit of priority of Japanese Patent
Application Number 2014-086009 filed on Apr. 18, 2014, the entire
contents of which are hereby incorporated by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] The present disclosure relates to a light receiving device
that converts incident light into an electrical signal, and, in
particular, to a light receiving device including a semiconductor
scanning circuit for reading the signal charge converted from the
incident light by a photodiode having a photoelectric conversion
function.
[0004] 2. Description of the Related Art
[0005] A light receiving device has been conventionally developed
and commercialized, in which a photodiode of a photoelectric
converter and a scanning element that transfers photoelectric
charges generated by the photodiode are integrated on a
semiconductor substrate.
[0006] In the conventional light receiving device, the photodiode
and the scanning element are disposed on the same plane. Hence, the
aperture ratio (the ratio of the amount of light incident on the
photoelectric converter to the amount of light incident on the
light receiving surface) is small. This results in low light use
efficiency and large loss of incident light.
[0007] Although development of an on-chip microlens, for example,
has increased the substantial aperture ratio, increase in the
substantial aperture ratio is limited as long as the photodiode and
the scanning element are disposed on the same plane.
[0008] In view of the above, a light receiving device has been
proposed in which a photodiode for generating photoelectric charges
are stacked on the scanning circuit substrate for photoelectric
charge transfer.
[0009] Since the photodiode serving as a light receiving portion is
disposed on the entire surface of the scanning circuit in the light
receiving device, the light receiving device can have an aperture
ratio close to 100%, which leads to increased sensitivity.
[0010] In order to achieve good optical response characteristics,
such a light receiving device generally has an electrode which
contacts the photodiode in such a manner that charge injection is
blocked.
[0011] Therefore, in a light receiving device which does not use
charge multiplication within the device, it is not possible to take
out the signal charges exceeding the number of carriers generated
by incident light. This results in the gain of the photoelectric
conversion being one or less.
[0012] In view of the above, a light receiving device having a
photoelectric conversion gain exceeding one, an avalanche
multiplication type light receiving device has been developed. In
this device, an avalanche multiplication phenomenon is generated by
applying a strong electric field to the photodiode to make the gain
of the photoelectric conversion one or greater.
[0013] In such an avalanche multiplication type light receiving
device, the gain which is the ratio of the number of photoelectric
charges generated within the photodiode to the number of incident
photons ranges from several dozen to several hundred.
[0014] The stacked light receiving device described above is formed
by forming, on a silicon substrate, a scanning circuit through the
semiconductor processes used for a general integrated circuit and
sequentially depositing a photodiode and a transparent conductive
film on the scanning circuit.
[0015] In this case, before the transparent conductive film is
formed on the scanning circuit, the scanning circuit is formed
through complicated processes performed on a silicon substrate.
Hence, it is extremely difficult to smooth the surface of the
scanning circuit before the transparent conductive film is formed,
which results in that the pixel electrode itself or the boundary of
the pixel electrode has unevenness.
[0016] Therefore, for example, unlike a photoconductive type image
pickup tube where a photoconductive film is formed on a smooth
glass substrate, dark current increases due to a local electric
field concentration caused by unevenness of the base, which is
likely to lead to white spot defects appearing on the screen.
[0017] In particular, if it is desired to obtain high sensitivity
by using the avalanche multiplication phenomenon in a photodiode,
it is necessary to apply a strong electric field to the photodiode.
Hence, local dark current injection or avalanche breakdown due to
non-uniformity of the electric field is likely to occur.
[0018] As a conventional technique for solving the above problems,
for example, Japanese Unexamined Patent Application No. H7-192663
(hereinafter, referred to as patent literature (PTL) 1) discloses a
structure in which a photoelectric converter, including a
transparent conductive film and a photodiode formed on a light
transmitting substrate, is connected, via conductive microbumps, to
signal reading electrodes of a scanning circuit formed on a
substrate different from the light transmitting substrate.
[0019] FIG. 9 is a cross-sectional view of a photoelectric
converter of a conventional light receiving device. Transparent
conductive film 103 and, photodiode 104 are formed on light
transmitting substrate 113. First pixel electrodes 105 having a
predetermined size are arranged on the surface of photodiode 104 at
predetermined intervals. Second pixel electrodes 107 are provided
on the surface of scanning circuit 108 at the same pitch as first
pixel electrodes 105. Microbumps 106 for electrically connecting
photoelectric converter 101 and scanning circuit 102 are provided
on second pixel electrodes 107.
[0020] As illustrated in FIG. 9, the light receiving device
according to the conventional technique has a structure where
photoelectric converter 101 and scanning circuit 102 separately
formed are electrically connected by microbumps 106 as described
above.
[0021] In the conventional technique, for example, a substrate
which is polished to have a sufficiently fiat surface is used.
Accordingly, photodiode 104 is formed on a significantly flat
base.
[0022] Thus, for example, even if a light receiving device is
operated by applying, to a photodiode, a high electric field which
causes charge multiplication in the photodiode due to an avalanche
phenomenon, an increase in dark current or an avalanche breakdown
due to local electric field concentration is unlikely to occur.
[0023] Moreover, since scanning circuit 102 and photoelectric
converter 101 are formed separately, the materials for second pixel
electrodes 107 on scanning circuit 108 and for photodiode 104 can
be selected without considering the electrical connection
characteristics of second pixel electrodes 107 and photodiode
104.
[0024] In other words, optimal materials, structures, and
manufacturing methods can be used without any constraints imposed
by being a stacked image capturing device.
[0025] Therefore, in such a stacked structure using the microbumps,
for example, as a substrate on which a photodiode is formed, an SOI
(Silicon On Insulator) substrate is used which has a silicon oxide
film disposed between a silicon substrate and a surface silicon
layer. The SOI substrate is effective for a reduction in parasitic
capacitance of a transistor, an increase in operating speed, and a
reduction in power consumption. Silicon and the silicon oxide film
are removed after stacking the scanning circuit and the microbumps,
and a transparent conductive film is formed. In this way, the
characteristics of the photodiode can be further improved.
SUMMARY
[0026] However, when the light receiving device is operated by
applying, to a photodiode, a high electric field which causes
charge multiplication in the photodiode due to an avalanche
phenomenon, a voltage needs to be supplied to the transparent
conductive film on the photodiode. However, PTL 1 does not mention
how to supply the voltage, and thus, users are not sure of how to
supply the voltage.
[0027] Japanese Unexamined Patent Application No. 2005-539218
(hereinafter, referred to as PTL 2) discloses a structure for
supplying a voltage to a transparent conductive film. For example,
as illustrated in FIG. 10, transparent conductive film 103 is
connected to electrode pad 110 of scanning circuit 102 to allow
external voltage application.
[0028] However, when transparent conductive film 103 is formed at
the stepped portions of housing 114 in the above structure,
transparent conductive film 103 may be thinner at the side wall
portion than at the upper surface portion depending on the
processing method. Non-uniform thickness of transparent conductive
film 103 leads to unstable voltage supply, making it difficult to
provide desired charge multiplication effects and high
sensitivity.
[0029] Additionally, there is a risk of breakage/disconnection of
the transparent conductive film due to stress concentration at the
corner of the housing.
[0030] In order to solve the above problems, the light receiving
device according to an aspect of the present disclosure includes: a
photoelectric converter including a photodiode and a pixel
electrode disposed on a lower surface of the photodiode; a scanning
circuit connected to the pixel electrode; an electrode pad disposed
on a periphery of the scanning circuit; and a transparent
conductive film extending from an upper surface of the photodiode
to the electrode pad, the transparent conductive film having an
inclination relative to the upper surface of the photodiode,
between the photodiode and the electrode pad.
[0031] In the light receiving device according to an aspect of the
present disclosure, the transparent conductive film is not bent
sharply at the corner of the edge of the upper surface of the
photoelectric converter. Hence, it is possible to reduce
disconnection of the transparent conductive film due to stress
concentration at the corner.
[0032] Moreover, since the transparent conductive film has a
uniform thickness on the upper and side surfaces of the
photoelectric converter, stable voltage supply can be provided. As
a result, a highly sensitive sensor with less image unevenness can
be provided.
BRIEF DESCRIPTION OF DRAWINGS
[0033] These and other objects, advantages and features of the
disclosure will become apparent from the following description
thereof taken in conjunction with the accompanying drawings that
illustrate a specific embodiment of the present disclosure.
[0034] FIG. 1 is a cross-sectional view of a light receiving device
according to Embodiment 1.
[0035] FIG. 2 is a top view of the light receiving device according
to Embodiment 1.
[0036] FIG. 3A is a cross-sectional view of a manufacturing process
of the light receiving device according to Embodiment 1.
[0037] FIG. 3B is a cross-sectional view of the manufacturing
process of the light receiving device according to Embodiment
1.
[0038] FIG. 3C is a cross-sectional view of the manufacturing
process of the light receiving device according to Embodiment
1.
[0039] FIG. 3D is a cross-sectional view of the manufacturing
process of the light receiving device according to Embodiment
1.
[0040] FIG. 4 is a cross-sectional view of a light receiving device
according to Variation of Embodiment 1.
[0041] FIG. 5 is a cross-sectional view of a light receiving device
according to Embodiment 2.
[0042] FIG. 6 is a top view of the light receiving device according
to Embodiment 2.
[0043] FIG. 7 is a cross-sectional view of a light receiving device
according to Embodiment 3.
[0044] FIG. 8A is a cross-sectional view of a manufacturing process
of a light receiving device according to Embodiment 3.
[0045] FIG. 8B is a cross-sectional view of the manufacturing
process of the light receiving device according to Embodiment
3.
[0046] FIG. 8C is a cross-sectional view of the manufacturing
process of the light receiving device according to Embodiment
3.
[0047] FIG. 8D is a cross-sectional view of the manufacturing
process of the light receiving device according to Embodiment
3.
[0048] FIG. 9 is a cross-sectional view of a photoelectric
converter of a light receiving device according to a conventional
technique.
[0049] FIG. 10 is a cross-sectional view of the photoelectric
converter of the light receiving device according to a conventional
technique.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0050] Hereinafter, embodiments for carrying out the present
disclosure will be described with reference to the drawings.
However, detailed descriptions may be omitted. For example,
detailed descriptions of well-known aspects or repetitive
descriptions of essentially similar configurations may be omitted.
This is to avoid redundancy and make the following description
easier for those skilled in the art to understand.
[0051] Note that the accompanying drawings and the following
description are provided not to limit the subject matter of the
claims, but to aid those skilled in the art to adequately
understand the present disclosure.
Embodiment 1
[0052] FIG. 1 is a cross-sectional view of a light receiving device
according to Embodiment 1 (a cross-sectional view taken along line
1-1 in FIG. 2 to be described later). The light receiving device
includes photoelectric converter 101, scanning circuit 102, and
microbumps 106. Photoelectric converter 101 and scanning circuit
102 are stacked via microbumps 106. In other words, the light
receiving device is a so-called stacked device.
[0053] The light receiving device according to Embodiment 1
illustrated in FIG. 1 will be described in more detail.
Photoelectric converter 101 includes: photodiode 104; and first
pixel electrodes 105 having a predetermined size and arranged on
photodiode 104 at predetermined intervals. Scanning circuit 102
includes: second pixel electrodes 107 formed at the same pitch as
first pixel electrodes 105; electrode pads 110; and dummy bumps 116
formed between second pixel electrodes 107 and electrode pads 110.
First pixel electrodes 105 and second pixel electrodes 107 are
connected by microbumps 106. Sealing resin 109 is formed in the
space around microbumps 106. Sealing resin 109 forms a smooth
fillet extending from dummy bump 116 and reaching the upper surface
of photodiode 104. That is, sealing resin 109 surrounding
photoelectric converter 101 has a fillet shape inclined relative to
the upper surface of photodiode 104. The fillet reaches the edge of
the upper surface of photodiode 104. Transparent conductive film
103 is formed on photodiode 104 and the fillet of sealing resin
109. Transparent conductive film 103 is connected to at least two
electrode pads 110 on scanning circuit 102.
[0054] As described above, transparent conductive film 103 extends
from the upper surface of photodiode 104 to electrode pads 110, and
has an inclination relative to the upper surface of photodiode 104,
between photodiode 104 and electrode pad 110. In particular, the
surface of sealing resin 109 between the edge of photodiode 104 and
electrode pad 110 is inclined relative to the upper surface of
photodiode 104 at 45 degrees or less. That is, the inclination of
transparent conductive film 103 relative to the upper surface of
photodiode 104 is at 45 degrees or less.
[0055] According to the light receiving device above, sealing resin
109 provided between photoelectric converter 101 and electrode pads
110 which are provided on the semiconductor substrate has an
inclination. Hence, transparent conductive film 103 is not bent
sharply at the corner of the edge of the upper surface of
photoelectric converter 101. This reduces disconnection of
transparent conductive film 103 due to stress concentration at the
edge of the upper surface of photoelectric converter 101.
[0056] Moreover, transparent conductive film 103 can have a uniform
thickness on the upper and side surfaces of photoelectric converter
101. This allows voltage to be stably supplied, leading to a highly
sensitive light receiving device with less image unevenness.
[0057] FIG. 2 is a top view of the light receiving device according
to Embodiment 1. Sealing resin 109 surrounds photoelectric
converter 101. Transparent conductive film 103 entirely covers
photoelectric converter 101 and sealing resin 109, and is connected
to electrode pads 110 on scanning circuit 102.
[0058] In photoelectric converter 101, photodiode 104 is formed,
for example, on an SOI substrate.
[0059] Scanning circuit 102 includes, on a per pixel basis, a MOS
transistor formed on a semiconductor substrate made of, for
example, silicon materials. The MOS transistor includes a charge
storage unit, a charge reading unit, and a gate electrode.
[0060] Transparent conductive film 103 includes, for example; tin
oxide (SnO.sub.2) containing antimony or fluorine as a dopant; zinc
oxide (ZnO) containing aluminum, gallium, indium, or tin as a
dopant; or indium oxide (In.sub.2O.sub.3) containing tin, tungsten,
or titanium as a dopant. An indium oxide film containing tin as a
dopant, that is, In.sub.2O.sub.3-Sn based film, referred to as ITO
(Indium Tin Oxide) film, is particularly preferable materials for
transparent conductive film 103 as the ITO film easily leads to a
transparent conductive film with a low resistance. Although an
epoxy-based or acryl-based underfill resin, for example, is used
for sealing resin 109, but the materials for sealing resin 109 are
not limited to such examples. Sealing resin 109 is formed in the
light of wettability and the like so that dummy bumps 116 prevent
sealing resin 109 from reaching electrode pads 110 on scanning
circuit 102.
[0061] Microbumps 106 are formed on first pixel electrodes 105 and
second pixel electrodes 107 as bumps (projecting electrodes) having
a height ranging from several .mu.m to several dozen .mu.m. Note
that microbumps 106 can be manufactured by several ways including
plating process and photolithography process.
[0062] The materials for microbumps 106 are required to be
conductive materials with a resistance that is as low as possible.
Examples of the low-resistance metal materials include Sn, Cu, Au,
Ni, Co, Pd, Ag, and In. Examples of the structure of microbumps 106
include a single layer structure including any one of the above
metal materials, a multilayer structure of layers of different
metal materials, and a structure including an alloy of the above
metal materials.
[0063] Moreover, as micro bumps 106, a paste formed by mixing the
conductive particles in an adhesive may be used. Examples of such a
paste include (i) Ag paste or Ag--Pd paste printed on a reading
electrode and (ii) metal, such as Au, elemental In, and alloyed In
etc. having good ductility and high adhesion, formed on a reading
electrode in a pillar shape or a conical shape. As microbumps 106,
a conductive paste may also used. The structure under the bumps may
be, for example, an Al or SiN film as long as a seed layer can be
formed.
[0064] FIG. 3A to FIG. 3D are cross-sectional views in respective
manufacturing processes of the light receiving device according to
Embodiment 1.
[0065] As illustrated in FIG. 3A, first, the positions of dummy
bumps 116 on scanning circuit 102 and microbumps 116 on the pixel
electrodes of scanning circuit 102 and photoelectric converter 101
including photodiode 104 formed over silicon substrate 111. and
silicon oxide film 112 are adjusted to desired positions. After
that, microbumps 106 on the pixel electrodes of scanning circuit
102 and microbumps 106 on the pixel electrodes of photoelectric
converter 101 are brought into contact with each other and
connected to each other.
[0066] Next, as illustrated in FIG. 3B, silicon substrate 111 and
silicon oxide film 112 are removed by a wet process or a dry
process, to expose photodiode 104.
[0067] Next, as illustrated in FIG. 3C, for example, epoxy-based
sealing resin 109 is injected to the peripheral edge portion of
photoelectric converter 101 and, a space between photoelectric
converter 101 and scanning circuit 102, and is cured at a constant
temperature to be resin molded.
[0068] Next, as illustrated in FIG. 3D, transparent conductive film
103 is formed over photodiode 104, the fillet of sealing resin 109,
and scanning circuit 102 by vapor deposition. Subsequently, an
unnecessary portion of transparent conductive film 103 is removed,
and unremoved transparent conductive film 103 is connected to
electrode pads 110 on scanning circuit 102.
[0069] According to the light receiving device described above,
sealing resin 109 provided between photoelectric converter 101 and
electrode pads 110 which are provided on a semiconductor substrate
has an inclination. Hence, transparent conductive film 103 is not
bent sharply at the corner of the edge of the upper surface of
photoelectric converter 101. This reduces disconnection of
transparent conductive film 103 due to stress concentration at the
edge of the upper surface of photoelectric converter 101.
[0070] Moreover, transparent conductive film 103 can have a uniform
thickness on the upper and side surfaces of photoelectric converter
101. This allows voltage to be stably supplied, leading to a highly
sensitive light receiving device with less image unevenness.
[0071] (Variation)
[0072] FIG. 4 is a cross-sectional view of a light receiving device
according to Variation of Embodiment 1. Transparent conductive film
103 is formed on, instead of sealing resin 109 forming a fillet, a
side surface of housing 120 which has an opening at the position
corresponding to the upper surface of photodiode 104 and which
surrounds photoelectric converter 101. Transparent conductive film
103 is connected to electrode pads 110 on the periphery of scanning
circuit 102. Housing 120 is provided on scanning circuit 102.
Housing 120 has a side surface which has an inclination relative to
the upper surface of photodiode 104, in particular, at 45 degrees
or less.
[0073] As described above, in the light receiving device according
to Variation, scanning circuit 102 has housing 120. Housing 120 has
a side surface surrounding photoelectric converter 101 and having
an inclination relative to the upper surface of photodiode 104.
Transparent conductive film 103 is formed on the side surface of
housing 120.
[0074] With this structure, the same advantageous effects as the
light receiving device according to Embodiment 1 can be obtained.
Moreover, with this structure, housing 120 allows transparent
conductive film 103 having a desired inclination to be more
reliably formed.
Embodiment 2
[0075] FIG. 5 is across-sectional view of a light receiving device
according to Embodiment 2.
[0076] Protective film 117 is formed. instead of dummy bumps 116
according to Embodiment 1, so that sealing resin 109 does not reach
electrode pads 110 on scanning circuit 102.
[0077] FIG. 6 is a top view of the light receiving device according
to Embodiment 2. Sealing resin 109 surrounds photoelectric
converter 101. Transparent conductive film 103 entirely covers
photoelectric converter 101 and sealing resin 109, and is connected
to electrode pads 110 on scanning circuit 102.
[0078] Photolithography and etching are performed on the outermost
surface protective film of scanning circuit 102 using a gray-scale
mask, so that the protective film has a projection. Since
protective film 117 is simultaneously formed when etching the
protective film on electrode pads 110, the number of processes does
not increase.
[0079] Sealing resin 109 forms a smooth fillet extending from
protective film 117 to the edge of the upper surface of photodiode
104. The inclination of the fillet relative to the main surface of
scanning circuit 102 is at 45 degrees or less.
[0080] According to the structure in Embodiment 2, the same
advantageous effects as the light receiving device according to
Embodiment 1 can be obtained.
Embodiment 3
[0081] FIG. 7 is a cross-sectional view of a light receiving device
according to Embodiment 3.
[0082] The light receiving device according to Embodiment 3 has a
stacked device structure where first pixel electrodes 105 of
photoelectric converter 101 and second pixel electrodes 107 of
scanning circuit 102 are connected via microbumps 106. Sealing
resin 109 is formed from dummy bump 116 to the space around
microbumps 106. Sealing resin 109 extends over silicon nitride film
115 on the upper surface of photoelectric converter 101.
[0083] The area over which silicon nitride film 115 extends is an
optical black area which defines the level of "black" of a pixel
value. Sealing resin 109 has a light shielding effect for
photodiode 104. In other words, sealing resin 109 serves as a light
shielding film. Moreover, stress concentration can be further
alleviated by sealing resin 109 covering the corner edge portion
which is a part of the upper surface of photoelectric converter 101
(photodiode 104).
[0084] Sealing resin 109 forms a smooth fillet extending from dummy
bump 116 to the upper surface of photodiode 104. The inclination of
the fillet relative to the main surface of scanning circuit 102 is
at 45 degrees or less.
[0085] FIG. 8A to FIG. 8D are cross-sectional views in respective
manufacturing processes of the light receiving device according to
Embodiment 3.
[0086] As illustrated in FIG. 8A, first, the positions of dummy
bump 116 on scanning circuit 102 and microbumps 106 on the pixel
electrodes of photoelectric converter 101 and scanning circuit 102
are adjusted to desired positions. After that, microbumps 106 on
the pixel electrodes of photoelectric converter 101 and microbumps
106 on the pixel electrodes of scanning circuit 102 are brought
into contact with each other and connected to each other. Here,
photoelectric converter 101 including photodiode 104 and first
pixel electrodes 105 is formed on silicon oxide film 112a into
which silicon nitride film 115 is embedded. Silicon oxide film 112a
is formed on silicon oxide film 112. Silicon oxide film 112 is
formed on silicon substrate 111.
[0087] Next, as illustrated in FIG. 8B, silicon substrate 111,
silicon oxide film 112, and silicon oxide film 112a are removed by
wet etching or dry etching, to expose photodiode 104. Silicon
nitride film 115 is left on the upper surface of photodiode 104 due
to a difference in etching rate.
[0088] Next, as illustrated in FIG. 8C, for example, epoxy-based
sealing resin 109 is injected to the peripheral edge portion of
photoelectric converter 101 and a space between photoelectric
converter 101 and scanning circuit 102, and covers the upper
surface of photoelectric converter 101 to the position where
silicon nitride film 115 is, and is cured at a constant temperature
to be resin molded.
[0089] Next, as illustrated in FIG. 8D, transparent conductive film
103 is formed over photodiode 104, the fillet of sealing resin 109,
and scanning circuit 102 by vapor deposition. Subsequently, an
unnecessary portion of transparent conductive film 103 is removed,
and unremoved transparent conductive film 103 is connected to
electrode pads 110 on scanning circuit 102.
[0090] With the structure according to Embodiment 3, the same
advantageous effects as the light receiving device according to
Embodiment 1 can be obtained.
[0091] In Embodiments 1 to 3 and Variation above, the light
receiving device may further include a unit for applying, to
photodiode 104, a voltage having a magnitude which causes charge
multiplication effect in photodiode 104. In other words, photodiode
104 may be an avalanche diode.
[0092] Although only some exemplary embodiments of the present
disclosure have been described in detail above, those skilled in
the art will readily appreciate that many modifications are
possible in the exemplary embodiments without materially departing
from the novel teachings and advantages of the present disclosure.
Accordingly, all such modifications are intended to be included
within the scope of the present disclosure.
INDUSTRIAL APPLICABILITY
[0093] The present disclosure is applicable to, for example, a
light receiving device required to have a small size, high
performance, high sensitivity, and low cost.
* * * * *